A thin film battery is a battery that is manufactured to a thin thickness by making basic components of the battery into thin films.
The thin film battery is a solid-state battery in which all of a cathode, an electrolyte and an anode are in a solid state and are formed to a thickness of several micrometers (μm) on a thin substrate by a deposition process, such as CVD, PVD, or the like.
With the use of a solid electrolyte, the thin film battery has various advantages, such as low risk of explosion, excellent thermal stability, low discharge rate, and the like.
FIG. 1 schematically shows a typical thin film battery.
Referring to FIG. 1, the typical thin film battery includes a cathode current collector 110, a cathode active material 120, an anode current collector 130, an electrolyte 140, and an anode active material 150.
In addition, the thin film battery is generally provided with an encapsulation member which encapsulates the remaining components except terminals of the cathode and anode current collectors 110, 130 in order to prevent moisture-penetration into the battery.
Here, in the case of a typical thin film battery, the anode current collector 130 and the electrolyte 140 overlap each other, and the anode active material 150 is not brought into direct contact with a substrate 100.
However, when the anode current collector 130 and the electrolyte 140 overlap each other, the thin film battery suffers from a phenomenon of lithium collection in a region where the two components overlap each other.
Such lithium-collection can cause cracking of an encapsulation film, so that moisture can penetrate into the battery through cracks. This results in oxidation of lithium on the side of the terminal of the anode current collector 130, thereby causing reduction in lifespan of the battery.